Sources of Slaves
Slaves usually came from the following sources:
Piracy and banditry: Depending on the era and geographical region, both piracy and banditry played a crucial part in providing a significant supply of slaves. If someone was caught by pirates or bandits, a ransom was to be paid for his or her release. If they were unable to pay, the prisoner was then sold to a slaver.
War: The war rules of the time were rather simple; the winner took it all. This rule applied to both civilians and soldiers. Many of them were recruited into slavery; sometimes even entire cities were made slaves.
Slave trade: According to historical sources, the main slave-trade centers were in the cities of Ephesus and Byzantium. Slaves being sold in these centers came from several sources such as piracy and banditry, but in some cases, parents sold their children into slavery as well. It is important to mention that nationality was very important for major slave buyers; they usually purchased slaves who had a different nationality, simply to avoid possible revolt.
How much did a slave cost? Naturally, the price of a slave was dependent on his or her abilities, age, appearance and overall attitude. For example, if a slave had quality characteristics, calculated in present value, he or she would cost around the equivalent of $180 American dollars. If there was a victory in war and a large amount of slaves suddenly appeared on the market, prices would go down accordingly.